Experiments were designed to assess the role of Marek's disease herpesvirus in the pathogenesis of arteriosclerosis in chickens. In one experiment a virus strain of low virulence and specific pathogen free (SPF) birds derived from a genetically susceptible line to Marek's disease were used. Two of the groups of birds were infected with the virus and three other groups remained as uninoculated controls. The groups were kept in separate isolation facilities. One virus group and one control group were given supplemental cholesterol midway in the experiment. The other groups remained on the low cholesterol diet. The birds in the five groups were recently euthanized. Systematic histological evaluation of all the collected hearts and aortas are currently underway and should be completed in a few months. A second experiment, similar in design, using chickens from a genetically resistant SPF line and a more virulent strain of virus is currently underway. The third experiment will be based on the histopathological findings on the hearts and aortas from the first experiment. A linkage of the Marek's herpesvirus in arteriosclerosis of chickens may be of great significance in understanding the human disease, particularly since similar herpesviruses are widely distributed in the human population.